DESCRIPTION: (Adapted From The Applicant's Abstract.) The degree of success and satisfaction experienced by cochlear-implant recipients varies greatly and is influenced significantly by the individual's ability to understand speech. It is hypothesized that the wide range of speech perception skills exhibited by cochlear-implant patients may be attributed, in part, to differences in central auditory processing abilities or in the capacity of the central auditory system to adapt to electrical stimulation. It is proposed to characterize speech-evoked cortical potentials in order to develop an objective measure of central auditory function in implant users. The long-term aim of this research is to develop a clinically feasible battery of speech--evoked electrophysiologic measures that can be used to evaluate the function of cochlear implants in deaf individuals. Optimally, that non-invasive test battery will be useful in assessing implant performance in patients who cannot undergo conventional behavioral testing (e.g. young children) and in providing a neurophysiologic basis for the design of rehabilitation programs and future implant signal-processing strategies. Specifically, the mismatch negativity (MMN)- a passively elicited evoked potential that reflects the cortical processing of fine acoustic stimulus differences - and the P300 cognitive potential will be investigated. Synthesized pairs of speech stimuli with well-defined acoustic parameters will be used to elicit the MMN and P300 in normal-hearing listeners and cochlear-implant patients to characterize the central neurophysiologic processes underlying normal and cochlear-implant-mediated speech perception. Those responses will be correlated with behavioral speech discrimination and related to clinical measures of speech perception and implant success. A subset of newly implanted adults and children will undergo the same battery of tests periodically for 12 months immediately after implantation to assess short-term longitudinal changes in electrophysiologic responses, auditory discrimination, and speech perception.